Antialiasing textures in cycles (Blender 2.77 and higher)
This is not exactly a solution, but I highly recommend a program called 'Substance Painter 2' - it lets you do fantastic mapping and texturing for a relatively low price, You can trial it for 30 days free, and it bakes normal maps, AO etc all with AA much better than Blender does.

I actually gave up trying to bake normals with Blender, as the results always had errors and artifacts. Substance Painter made it really easy, I didn't have to use a cage anymore, and it was worth every dollar.

I got it via steam at 50% off a couple of months ago, so if you can't afford it now and you have steam, put it on your wish list.

Regards, C.